From garden ponds filled with Koi Carp to the humble goldfish bowl (although goldfish are far happier living in a larger tank) – the UK is a nation of fish lovers.
There are an remarkable five million indoor fish tanks in the UK alone, according to the Pet Food Manufacturers’ Association (PFMA).
That’s about 10 per cent of British households – making fish the third most popular pet after dogs and cats.
It’s a fascinating hobby, particularly for youngsters, and there are few more relaxing activities than watching fish slowly swim around their home.
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There’s plenty of choice when it comes to adding fish to (well prepared and correctly set up) home aquariums, with pet shops offering a bewildering range of colourful and interesting finned friends that will happily live in the corner of your living room.
One of the most important things to note when choosing a new pet fish is whether they are likely to be aggressive - bullying, nipping or even eating their tankmates.
Many fish can co-exist happily with numerous other breeds in so-called community tanks, while others should be kept alone, with other fish of the same breed, or with breeds that are similarly aggressive.
Here are the 18 least, and most, aggressive breeds of popular tropical freshwater fish.
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5. Jack Dempsey Fish
Originally from Central American countries like Mexico and Honduras, the Jack Dempsey Fish is named after a famous 1920s boxer thanks to its fearsome face and aggressive nature. Best kept alone in a tank, it's also important to provide them with somewhere to hide away. | Canva/Getty Images
6. Texas Cichlid
The Texas Cichlid is aggressive, territorial, and intolerant of most tankmates - this is a creature not in the market for making fishy-friends. It often attacks competely indiscriminately and without warning, especially when it has breeding on its mind. Its strength and persistence make it difficult to manage in mixed setups. | Canva/Getty Images
7. Pea Puffer
The Pea, or Dwarf, Puffer is one of numerous species of Puffer Fish - and one particularly popular with aquarium owners. Some are tremendously toxic and all tend to display aggression to tank-buddies. Keep them away from other fish though and they make fascinating pets. | Canva/Getty Images
8. Peacock Bass
The Peacock Bass is a fish for serious aquariasts only - needing at least a 150 gallon tank. A predatory species, if they get peckish they'll eat pretty much anything put in front of them, including other Peacock Bass. | Canva/Getty Images